The present invention relates generally to a control for a wire feeder of a welding-type system. Specifically, the invention accepts a user selected mode, a current, and a voltage and then maintains the user selected current and voltage according to the user selected mode. The invention includes a control to allow the user to adjust a wire feed speed manually or allow the control to adjust the wire feed speed according the user-selected voltage and/or current inputs.
Wire feeders are typically used to feed metal wire into a weld during a welding process such as Gas Metal Arc Welding (GMAW) and other welding processes. Typical wire feeders have a drive roller assembly for driving the metal feed from a feed spindle through a welding gun for introduction to the weld. Power is supplied to the drive roller assembly by a welding power supply via a weld cable. The amperage or current generated by the power supply governs the speed in which the metal feed is fed to the weld, or the wire feed speed (WFS). Generally, the higher the amperage supplied to the wire feeder, the greater the WFS. Conversely, if voltage is used to govern the WFS, the lower the voltage, the higher the WFS. Accordingly, the speed by which the wire feeder supplies the metal filler to the weld is a direct function of the power delivered to the wire feeder and therefore, the weld. Furthermore, by adjusting the WFS and holding either voltage or current constant, the adjustment to the WFS causes the non-constant value to be adjusted accordingly.
The thickness of the metal being welded determines the power required at the weld and thus the WFS necessary to deliver that power. A thicker metal requires higher power to effectively weld. The wire feeder includes a wire feed control to control the power delivered to both the wire feeder and the point of the weld. Typically, the wire feed control allows the welding system to operate in at least one of two modes; either constant voltage (CV) or constant current (CC).
Should the user choose CV mode, as is most common in the United States, a user selected voltage is required. The voltage is an indication of the voltage desired at the point of the weld and is held constant by the power supply. It is also necessary to select an initial WFS. The WFS indicates the speed with which the metal filler is delivered to the point of the weld but when the mode is CV, also corresponds to an output current. By holding the output voltage constant, the user can manipulate the output current by adjusting the WFS. Since the WFS is directly proportional to the current delivered to the wire feeder and point of the weld, the higher the WFS, the greater the current delivered to the weld. However, should the user choose CC, as is common internationally, the user input current is held constant and the user can adjust the WFS to obtain the desired voltage at the weld. In this case, the user must lower the WFS in order to raise the voltage at the weld or raise the WFS to lower the voltage at the weld.
To enable a user to select the appropriate WFS, wire feed controls include a voltmeter, an ammeter, a wire-speed meter or a combination thereof. Should a voltmeter and ammeter be included, the user selects the desired mode, for instance CV. The user then selects the desired voltage and initial WFS. By viewing the current delivered on the ammeter, the user can manually adjust the WFS until the ammeter displays the desired current.
However, some wire feed controls include only a voltmeter, if CV, or only an ammeter, if CC. In this case, a wire-speed meter is included. In the case of a CV welding system, the user selects the desired voltage and the appropriate WFS is discerned from a look-up table. The look-up table is a listing of output current values and corresponding WFS. By finding the desired current in the look-up table, the user can discern the associated WFS required to deliver the desired current to the weld.
However, by requiring the user to manually adjust the WFS, human error is possible. Furthermore, the current delivered to, and the voltage at, the weld varies according to the conditions at the weld. As such, it may be necessary to adjust the WFS during the welding process to maintain the desired output conditions. Therefore, whether through human error or a varying load, it is possible to have an incorrect WFS and thus, an incorrect amount of power delivered to the weld. If the weld is underpowered, the weld will probably be insufficient to adequately join the materials being welded. On the other hand, if the weld is overpowered, it is possible to “burn through” the materials being welded.
It would therefore be desirable to have a system and method capable of delivering the desired current and voltage by adjusting the WFS automatically. The system and method would alleviate the reliance upon human intervention when adjusting the WFS and lower the possibility of insufficient welds or “burn throughs” due to varying loads.